Percussion fuse for projectiles



7 June 1943a w, PATCHETT 2,322,543

PERCUSSION FUSE FOR PROJECTILES Filed Oct. 8, 1940 if \NVE'NTOR (vEORCvE WILLIAM PATcHETT ATTYS."

Patented June 22, 1943 PERCUSSION FUSE FOR PROJECTILES George William Patchett, Egham, England Application October 8, 1940, Serial No. 360,321 In Great Britain October 9, 1939 9 Claims.

This invention is for improvements in or relating to percussion fuses for projectiles of the kind in which a striker can be moved into alignment with an igniting cap only by the rotary action of the projectile and thus the fuse can only become operative after the projectile has commenced its flight.

An object of the invention is to prevent the fuse from becoming operative until an appreciable time after the projectile has left the firearm.

According to this invention, a percussion fuse of the kind referred to above for a projectile is characterised in that the striker comprises a gyroscopic element having a stem or shaft one end of which is adapted to operate as a striker pin, which element is initially assembled in a compartment in the fuse or projectile with the stem or shaft extending transversely to the axis of rotation of the projectile and with the end of the striker pin located to one side of an axially disposed igniting cap and in that friction means are arranged to transmit the rotation of the projectile to the gyroscopic element. With this arrangement, when the projectile commences its travel through the firearm, rotation in space is imparted to the gyroscopic element by the aforesaid friction means which overcome the inertia forces tending to maintain the element stationary. The resulting centrifugal force on the element tends to bring its stem into axial alignment with the igniting cap but this force sets up a gyroscopic couple which imparts a precessional movement to the stem and it is some little while before the stem is brought into alignment with the igniting cap. When in alignment the gyroscopic element is in a condition to strike the cap when the fuse impacts upon a body in the path of its flight.

The aforesaid gyroscopic element may be initially disposed in the compartment either with its stem inclined to the axis of rotation of the projectile or with the stem at right-angles to said axis of rotation. In this latter case it is necessary for the gyroscopic element to be so formed that it has three principal axes of inertia at right-angles to one another and initially arranged with an unstable median axis of inertia in alignment with the axis of rotation of the projectile. Thus, the effect of the rotation of the projectile is first to bring the stem in inclined relationship to the axis of rotation and then to bring it into axial alignment.

Preferably detent means are provided for hold- 7 ing the gyroscopic element with the striker pin in the inoperative position until the firearm is fired whereupon the gyroscopic element is released. Thus, there is no fear of the fuse becoming operative during handling. The said detent means may be arranged to be released by centrifugal force or by inertia forces due to the acceleration of the projectile. For example, the detent may comprise an abutment on an axially movable impact member arranged at the forward end of the gyroscopic element and initially held in position by a radially movable element infiuenced by the aforesaid centrifugal or other inertia forces.

In one constructional form of the invention the stem of the gyroscopic element may be arranged between two abutment faces one of which is fiat and the other of which is concavely spherical which abutments are relatively movable in an axial direction but are initially returned by said detent in a position in which the gyroscopic element is inoperative. The flat faced abutment may be arranged in the projectile to the rear of the other abutment and is provided with a central aperture arranged in line with the igniting cap and the said spherical faced abutment may be associated with the aforesaid impact member. The forward end of the stem of the gyroscopic element and the periphery of the body of the element may be provided with spherical surfaces arranged to engage the spherical face of the abutment.

Other features of the invention are set out below.

The following is a description of two alternative forms of percussion fuse according to this invention, reference being made to the accompanying drawing, in which:

Figure 1 is a section through the end of a. projectile showing the fuse in position,

Figure 2 is a similar view showing an alternative form of fuse, and

Figure 3 is a side elevation of the gyroscopic element employed in the construction shown in Figure 2.

Referring now to the construction shown in Figure 1, the projectile I0 is provided at the forward end with the usual screw-threaded recess H for accommodation of the fuse body I2 and is also provided with a passage l3 communicating with the explosive chamber M of the projectile which passage accommodates the primer 15. An igniting cap is centrally disposed in the forward end of the primer but is not shown in the drawing. The striker for the cap is in the form of a gyroscopic element 16 which is disposed in a compartment I! formed in the base of the fuse body I2. The stem of the gyroscopic element has one end formed as a striking pin Hi. When initially assembled the gyroscopic element is arranged with its stem inclined to the axis of the projectile and so that the end of the striking pin and a part of the periphery of the gyroscopic element rest on a fiat abutment washer l9 which forms a closure for the aforesaid compartment IT. The other end of the stem is provided with a spherical surface 29 which is concentric with a spherical surface 2| formed on the periphery of the gyroscopic element. These two spherical surfaces are frictionally engaged by a spherical abutment face 22 formed on the head 23 of an impact member having a forwardly-extending hollow shaft 24. The hollow shaft is accommodated in a bore 25 formed in the nose of the fuse the forward end of which bore is closed by a thin metal disc 25 located in a groove in said bore. A' radial passage 21 is formed in the body of the fuse in such a position that when the fuse is screw-formed in the projectile the end of the passage is obscured by the projectile. Located in the radial passage is a centrifugal element 28 in the form of a small spring the convolutions at one end of which are compressed at 29 to form a loading weight, which compressed convolutions are arranged opposite the shoulder formed between the head 23 of the impact member and the hollow shaft 24. The operation of the device is as follows. When the projectile is first fired and is passing through the barrel of the firearm the rotation of the projectile causes the small spring 28 to be compressed bringing the convolutions 29 out of alignment with the aforesaid shoulder. The acceleration of the projectile causes the impact member to press the gyroscopic element into frictional engagement with the fiat abutment washer whereby rotation is imparted to the element about the axis of the projectile. When the projectile enters the atmosphere deceleration takes place and the impact member and gyroscopic element move forwardly remaining in frictional engagement. The striker end of the stem is thus freed and the rotation imparted to the gyroscopic'element results in forces which cause the stem to align itself with the axis of the projectile and to'bring the striker pin I8 into alignment with the cap; thus, when the nose of the fuse comes into contact with an object it crushes and drives the impact member against the gyroscopic element so that the striker pin pierces the cap and explodes the projectile.

' Should the projectile not meet its mark and be nearing the end of its trajectory, its initial spin diminishes and the projectile no longer maintains its axis in alignment with the path of travel and may even be turning about a transverse axis. Under these conditions the impact member may return to its initial safe position and relock the gyroscopic element in its nonfiring condition. This is a great advantage in the case of projectiles used against aircraft, since it is probable that a spent unexploded projectile is rendered harmless before it reaches the ground. Referring now to the construction shown in Figures 2 and 3, the mechanism is housed in the nose of the projectile instead of in a fuse body as described above. The compartment which houses the gyroscopic element comprises a sheet metal casing 30 which is flanged inwardly at 3| at its forward end so as to form a guide for the hollow shaft 24 of the impact member. An outstand mg flange 32 is formed on the casing near its rearward end and is arranged to rest against a shoulder 33 formed in the hollow interior of the projectile whereby the compartment for the gyroscopic element may be correctly located. The rear end of the compartment is closed by an abutment washer 34 the periphery of which initially rests on a slotted circumferential ridge 35 pressed in the aforesaid casing. The resilient tongues formed by the slotting of the ridge 35 enable the washer to be fixed by axial pressure but it is prevented from leaving the casing by the forward end of the primer l5. The rear end of the casing is also provided with an inwardly turned lip 36. The gyroscopic element is formed from two sheet metal cup-shaped members 3'! having interfitting hub portions 38 and having outwardly-turned peripheral flanges 39. The inner hub 38 firmly embraces the stem 40 which projects equally on either side of the cupshaped members. Clamped between the twocup-shaped members and surrounding the outer hub is a loading disc 43 which is cut away at 4| at opposite ends of a diameter so as to provide an unstable medium axis of inertia. As distinct from the construction shown in Figure l the gyroscopic element is initially so located that its stem 45] extends at right-angles to the axis of the projectile. The washer 34 is provided with an upstanding hollow boss 42 which is located between the flanges 39 of the gyroscopic element and in one of the cut-away portions and thus prevents the element from tilting until the projectile is fired. When the projectile is fired the inertia forces first move the Washer axially beyond the ridge 35 against the end of the primer but the impact member 23 moves rearwardly and retains the gyroscopic element in the position shown in Figure 2 in frictional engagement with the washer. When the projectile entore the atmosphere and deceleration takes place the gyroscopic element moves forwardly with the impact member, while the rotation imparted to the gyroscopic element previously by the rotation of the projectile has the effect of causing the stem 10 to precess and to move into alignment with the axis of the projec 'le since the unstable axis of inertia tends to turn away the axis of rotation of the projectile. When the stem is in axial alignment one of the flanges 39 engages the spherical surface 22 whereby the stem Mi is maintained in axial alignment with the hole in the washer 34. Thus, when the projectile meets an object the stem strikes the cap and the projectile explodes.

I claim:

1. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap and the other end of. which is adapted to re.- ceive a strik ng force when the projectile strikes an object, detent means for holding said gyro-. scopic element in said housing with its. stem transversely disposed in relation to the axis of; rotation of the projectile and out of operative relationship with the cap, which detent means are adapted to be released by inertia forces set up by the firing of the projectile and friction means adapted to transmit rotation of the projectile to the gyroscopic element which housing andgyroscopic element are so shaped, and dimensioned as to permit during the flight. 0f the projectile, freedom of movement of the. gyroscopic element about twoaxes at right anglesto,

one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line,

2. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap asso ciated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap and the other end of which is adapted to receive a striking force when the projectile strikes an object, detent means for holding said gyroscopic element in said housing with its stem inclined to the axis of rotation of the projectile and out of operative relationship with the cap, which detent means are adapted to be released by inertia forces set up by the firing of the projectile and friction means adapted to transmit rotation of the projectile to the gyroscopic element which housing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyrosoopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line,

3. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap and the other end of which is adapted to receive a striking force when the projectile strikes an object, detent means for holding said gyroscopic element in said housing with its stem arranged at right-angles to the axis of the projectile and out of operative relationship with the cap, which gyroscopic element is so formed that it has three principal axes of inertia at right-angles to one another and is initially arranged with the unstable median axis of inertia in alignment with the axis of rotation of the projectile which housing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

4. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap, an impact member extending into said housing and adapted to engage the other end of said stem, detent means for holding said gyroscopic element in the housing with its stem transversely disposed in relation to the axis of rotation of the projectile and out of operative relationship with the cap, which detent means are adapted to be released by inertia forces set up by the movement of the projectile in the barrel which housing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

5. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap, an axially movable impact member extending into said housing and having an abutment face adapted frictionally to engage the other end of said stem and a peripheral face of the element, a closure for said compartment opposite the impact member and adapted to provide an abutment face for the striker end of said stem and a peripheral portion of the gyroscopic element and having an aperture through which said axis of rotation passes which hous ing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

6. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap, an axially movable impact member having a concavely spherical abutment face adapted frictionally to engage the other end of said stem and a peripheral face of the element, a closure wall for said compartment opposite the impact member and adapted to provide a fiat abutment face for the striker end of said stem and a peripheral portion of the gyroscopic element and having an aperture through which said axis of rotation passes which housing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

7. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing and having a stem one end of which is adapted to operate as a striker for said cap, an axially movable impact member extending into said housing and having an abutment face adapted frictionally to engage the other end of said stem and a peripheral face of the element, a closure Wall for said compartment opposite the impact member and adapted to provide an abutment face for the striker end of said stem and a peripheral face of the gyroscopic element, centrifugally operated detent means arranged to hold the axially movable abutment in such a position that the gyroscopic element is retained with the stem extending transversely to the axis of the rotation of the projectile, and having an aperture through which said axis of rotation passes which housing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

A percussion fuse for a projectile comprisin a housing, a holder for an igniting cap associ ted with said housing, a gyroscopic element in said housing having a stem one end of which is adapted to operate as a striker for the cap, an axially movable impact member extending into said housing and adapted to engage the other end of said stem, an axially movable wall for said housing arranged on the opposite side of said gyroscopic element to said impact member, detent means for retaining said wall in either of two positions in one of which the gyroscopic element is retained with said stem extending transversely in relation to the axis of rotation of the projectile and in the other of which the gyroscopic element is free to move into a position in which the striking end of the stem is in operative relation to said cap which housing and gyroscopic element are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to r0- tate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

9. A percussion fuse for a projectile comprising a housing, a holder for an igniting cap associated with said housing, a gyroscopic element in said housing having a stem one end of which is adapted to operate as a striker for said cap and the other end of which is adapted to receive a striking force when the projectile strikes an object, friction means adapted to transmit rotation of the projectile to the gyroscopic element, which gyroscopic element and housing are so shaped and dimensioned as to permit during the flight of the projectile, freedom of movement of the gyroscopic element about two axes at right angles to one another and at right angles to the axis of rotation of the element, also for the element to rotate relatively to the projectile, and also for the gyroscopic element as a whole to move along the axis of rotation of the projectile when the axis of rotation of the element and projectile are in line.

GEORGE WILLIAM PATCHETT. 

